POS0376 DOES A MANDATORY SWITCH FROM ORIGINATOR ADALIMUMAB TO BIOSIMILAR GP2017 OR SB5 LEAD TO INCREASED HOSPITAL COSTS? A DANBIO STUDY OF &gt;1,300 PATIENTS WITH INFLAMMATORY ARTHRITIS
Authors: H. Nabi, R. Ibsen, M. Ibsen, J. Kjellberg, M. L. Hetland, B. Glintborg
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> In 2018, Danish national guidelines dictated a mandatory switch from originator to biosimilar adalimumab based on geographical residence, i.e., GP2017 in Eastern regions and SB5 in Western regions of Denmark[1]. The switch was motivated by cost savings (approx. 34-49%). Concerns were raised if hospitals would encounter additional costs as a result of increased numbers of outpatient visits/contacts (due to patient concerns, education, treatment monitoring). <h3>Objectives</h3> To investigate if the switch from originator to either of the adalimumab biosimilars led to increased hospital costs, defined as all in- and outpatient contacts. <h3>Methods</h3> Observational cohort study with surrogate cluster (i.e. geographical) pseudo-randomization. Patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) or axial spondyloartritis (AxSpA), who performed an adalimumab biosimilar switch were identified in the rheumatology registry, DANBIO. Hospital contacts were identified through linkage to the National Patient Registry. Hospital costs (based on DRG tariffs) were reported 9 months pre- and post-switch. In addition, the difference between pre- and postswitch costs was estimated by a generalized estimation equations (GEE) model. Medication costs of adalimumab originator and biosimilars were not available, and thus not included in the model. <h3>Results</h3> 1,318 patients were included (51% male, mean disease duration 16 years) and switched to either GP2017 (n=621) or SB5 (n=695). Baseline characteristics for both treatment groups stratified by diagnosis are given in <b>Table 1.</b> Monthly hospital costs 9 months pre- and post-switch were largely similar or decreased post-switch (<b>Figure 1</b>). No increase was found in the adjusted analyses (GEE); hospital costs decreased post-switch (by approximately 15%) for GP2017 switchers, especially PsA (estimate 0.83; 95% CI 0.75-0.92) and AxSpA patients (estimate 0.85;0.77-0.93), whereas no significant changes were found for SB5 switchers (<b>Table 1</b>). <h3>Conclusion</h3> In this study of &gt;1,300 patient with inflammatory arthritis, we found no sign of increased healthcare hospital costs 9 months following a nationwide mandatory adalimumab originator to biosimilar switch. Our findings were strengthened by similar results regardless of whether patients switched to GP2017 or SB5. <h3>Reference</h3> [1]Nabi H, Georgiadis S, Loft AG, et al. Ann Rheum Dis, doi:10.1136/annrheumdis-2021-219951 <h3>Acknowledgements</h3> We thank all the Danish departments of rheumatology, which report to the DANBIO registry. Also the work of IT consultant Niels Steen Krogh, Zitelab Aps, who extracted data from DANBIO is acknowledged. <h3>Disclosure of Interests</h3> Hafsah Nabi Grant/research support from: Research grant from AbbVie, who had no influence on the data collection, statistical analyses or decision to submit. Other research grants: Sandoz, Rikke Ibsen: None declared, Michael Ibsen: None declared, Jakob Kjellberg: None declared, Merete L. Hetland Speakers bureau: Biogen, Celtrion, Janssen Biologics B.V, MSD, Pfizer, Samsung Bioepis, Consultant of: Biogen, Celtrion, Janssen Biologics B.V, MSD, Pfizer, Samsung Bioepis, Grant/research support from: AbbVie, Biogen, BMS, Eli Lilly Denmark A/S, Lundbeck Fonden, Novartis, Pfizer, Roche, Sandoz., Bente Glintborg Grant/research support from: BMS, Pfizer, Sandoz.